The present invention relates to hydraulic jacks for lifting loads such as motorized vehicles and other heavy objects and equipment. Specifically, the invention relates to a versatile modular hydraulic floor jack adapted to lift different types of vehicular load, while being configured at the same time to provide enhanced lateral stability.
Hydraulic floor jacks are known in the art. Typically, a hydraulic floor jack includes a hydraulic ram that is given a mechanical advantage by known means, namely, in which a hydraulic press is harnessed to convert a manual input force into an output force delivered by a piston, the output force being considerably magnified over the input force. The magnified piston force may be applied directly to elevate a load, or it may be utilized to pivot an elevation arm of the floor jack, which elevates the load in a pivoting action.
A number of different types of floor jack have been developed, each for a specialized purpose. For example, a point lift hydraulic jack has been developed which is useful for elevating a motor vehicle. This kind of hydraulic jack applies an upward load to the motor vehicle on what is effectively an upwardly applied point load. (In reality of course, the upwardly applied load is not a precise “point,” but rather a flat plate having a relatively small area, hence it is an “effective” a point load.) An effective point load is desirable, firstly, because a motor vehicle that has been elevated will always have at least two wheels on the ground. These two wheels may be braked so that, in combination with the effective point load, a stable and immovable three point support exists and the motor vehicle will not move or tip while elevated. However, the undercarriage of a motor vehicle typically has a complex shape so that, if a multiple point ram were used to elevate the vehicle, or if a large flat plate were used on the end of the ram, it is likely that the point of lift may shift from one point to another as the vehicle is elevated. This is highly undesirable because the user may not know which point on the underside of the vehicle will eventually be the point of load when the vehicle is fully elevated. Thus, the user may find out too late that an inappropriate point on the underside of the vehicle has become the point of load. The point at which load is applied may be inappropriate because it may buckle, or even worse, may break. For example, a user will try to avoid applying a point of hydraulic lift to a flat floor panel of the motor vehicle because the floor panel may bend out of plane or may be punctured by the hydraulic lift. Therefore, a hydraulic lifting jack with an effective point support is always desirable when lifting motor vehicles because this enables the user to position that point under a strengthened portion of the undercarriage of the vehicle that he knows will sustain the load.
On the other hand, other types of motorized vehicles require a floor lifting jack with different characteristics to allow a workman to gain access to their undercarriage. For example, snowmobiles, motor bikes, and some all-terrain-vehicles each have a relatively small and narrow plan area, and neither type can be lifted at one point to leave two other points on the ground to stabilize the vehicle. Rather, the shapes of these vehicles may require that they be lifted entirely and bodily off the floor while stability against tipping over is provided entirely by the jack itself. To this end, such vehicles are often constructed so that the undercarriage has a flat portion at the center of gravity, and, for this kind of case, hydraulic floor jacks have been developed that have a relatively wide and long “footprint” in contact with the floor. They also have relatively wide and long planar lifting platforms that allow the lifted vehicle to balance on the platform while under elevation. However, where the jack is the only point of support for the vehicle, there is always an increased risk that the jack itself may tipple over, with disastrous consequences. In this regard, some of the prior art jacks that perform this specialized lifting function are made with side wheels that are spaced as widely apart as possible to give as much lateral stability as possible. However, this solution results in a hydraulic jack that occupies a very large area “footprint,” which may add to the overcrowding of a small workshop.
Another example of a vehicle lifting jack is one required for certain lawn tractors or other vehicles that have a wheel base that is too wide to permit a jack to lift the entire vehicle off the floor as in the case of a motorbike or snowmobile. Rather, the front end must be lifted by the front two wheels while the vehicle pivots about the back two wheels. In cases such as this, the front two wheels are driven onto slings or stirrups that are tied into a central lifting arm, and the lifting load is applied to the wheels via the stirrups. The reason that the load is taken by the wheels in this design and not by a central platform to the undercarriage, is that the wheel base of such vehicles may be so short that, when fully lifted in front about the pivoting back wheels, the vehicle slopes upward at a considerable angle. Thus, any surface on the tractor that was flat when parked will slope at the same large angle when the tractor is elevated. This would tend to create a dangerous situation if the lifting were caused by a load applied to the undercarriage because the point of contact will substantially realign itself from horizontal as the vehicle is elevated, producing the possible very undesirable result that the jack slips out of engagement with the tractor. Therefore, loops or stirrups are provided to capture the wheels of the tractor. When elevated, the tractor wheels may freely realign themselves by rotating, without any adverse result on safety.
A noticeable problem that has arisen in the art is that many workshops, both commercial and private, may be required to possess all three types of hydraulic jack described above to deal with the various types of vehicle that must be serviced. This gives rise to issues of financial expense, and also to issues of overcrowding and storage in the workshop for a host of different hydraulic jacks. Moreover, even where all three types of jack are provided in a workshop, the kind that elevates a vehicle entirely off the floor always suffers the risk of instability for which no suitable solution is available.
Thus there is a need in the art for a solution to problems found in the prior art as described above. The present invention addresses these and other needs.